Pre-usb mounts required a special serial cable to drive the mount without a hand controller. Why would you do this? well in my case my EQ8 is remotely operated and its the only way to start up the mount from cold without having to be there to press a key, even to access pc-direct mode.
Others are keen users of other telescope control software such as EQMOD and Green Swamp Server, both of which add a heap of capabilities not available via the hand controller.
Playing catch-up, skywatcher have now provided a fully supported method of telescope control without a handset for older scopes and that is the rather keenly priced cable it needs